Phonon-mediated vs. Coulombic Back-Action in Quantum Dot circuits

TL;DR

This paper investigates how energy emitted from a biased quantum point contact affects a coupled quantum dot, revealing that both phonons and Coulomb interactions contribute to back-action depending on system geometry.

Contribution

It provides a detailed analysis of the back-action mechanisms in quantum dot circuits, distinguishing between phonon-mediated and Coulombic effects based on experimental conditions.

Findings

Energy emitted by biased QPC causes charge fluctuations in the quantum dot.

Both acoustic phonons and Coulomb interactions are involved in back-action.

The dominant back-action mechanism depends on geometry and coupling constants.

Abstract

Quantum point contacts (QPCs) are commonly employed to capacitively detect the charge state of coupled quantum dots (QD). An indirect back-action of a biased QPC onto a double QD laterally defined in a GaAs/AlGaAs heterostructure is observed. Energy is emitted by non-equilibrium charge carriers in the leads of the biased QPC. Part of this energy is absorbed by the double QD where it causes charge fluctuations that can be observed under certain conditions in its stability diagram. By investigating the spectrum of the absorbed energy, we identify both acoustic phonons and Coulomb interaction being involved in the back-action, depending on the geometry and coupling constants.